Property Value

IsOverwriteMode takes into account both the value of the InsertKeyMode property and the state of the user's keyboard. If InsertKeyMode is set to either On or Off, IsOverwriteMode will return false or true, respectively. If InsertKeyMode is set to InsertKeyMode, it will return the state of the INSERT key.

When IsOverwriteMode is false, MaskedTextBox will reject as invalid any character entry that would result in a violation anywhere in the mask. In explanation, if inserting a character would cause a character to be shifted over into a mask position where it would not be valid, the character insertion will be rejected.